Compared with a conventional direct seeding manner, pot seedling transplantation has the following major advantages: growth periods of vegetables can be shortened, crop arrangement is facilitated, land utilization is improved, and economic income is increased. A transplanted pot seedling has a strong root system and consistent flowering and maturation, which can facilitate subsequent stages, such as management and harvesting. Therefore, pot seedling cultivation and pot seedling transplanting have become increasingly popular among vegetable producers and flower producers. However, due to the lack of suitable auxiliary machines, pot seedling cultivation and transplanting have been labor-intensive industries for a long time, where the labor cost accounts for over 50% of the total production cost. Manual transplanting has high labor intensity, low work efficiency, and low transplanting quality, so that large-area transplantation can hardly be implemented. Consequently, the production scale is small, the production efficiency is low, and the development of related crop production in China is restricted. The transplanter not only can greatly reduce the labor intensity and the production cost, improve the work efficiency, transplanting quality and the survival rate of the pot seedling, but also improve the economic and social benefits. Therefore, there is an urgent need for the development of a system that implements the mechanization of pot seedling transplanting work.
The planting system is the core system of the transplanter. The planting system is used to plant the pot seedling into soil by a duckbill with better planting quality; the pot seedling comes from the pot seedling distributor or the artificial work. Most vegetable crops need to keep the perpendicularity of the planting pot seedling, and it is necessary to ensure the velocity of the relative rest. The theory of zero-speed seedling transplanting is to create a moment of relatively static state for each planting pot seedling in the case of continuous movement of the transplanter, in order to complete the planting under the still upright state of the pot seedling. Therefore, in the process of planting a pot seedling, the forward speed of the transplanter is equal to the horizontal velocity of the pot seedling planting moment and the opposite direction, so that the instantaneous absolute velocity of the pot seedling planting moment is zero. The pot seedling is stationary relative to the ground at this point, while the pot seedling is planted into the soil by the planting mechanism. The soil is then overlaid to complete the planting process. At present, the transplanter has a slow planting speed under the restriction of “zero speed seedling transplanting,” the planting speed is usually about 40 pot seedlings per minute.
A straight line planting device for a transplanter was disclosed in Chinese patent publication CN101715670A, including a transmission device, a planting device, a control mechanism and a rack, which are used to drill the hole, form the hole and plant the pot seedling. The transmission device comprises sprocket wheels, a gear, a shaft and a crank link mechanism, where the crank link mechanism is composed of a crank, a connecting rod, a push rod, a rack and bearings. The control mechanism is composed of a stop lever, a positioning plate, a right connecting rod and a left connecting rod, and the bracket is fixed on the rack by bolt connection. The driving power of the crank link mechanism is driven by sprocket, gear and shaft, and the reciprocating linear motion of the planting device is achieved by the motion of the crank link mechanism. The planting device is in a closed state when it moves to the top dead center. The pot seedling is put into the planting device by the seedling feeding device, while the planting device drills into the soil near the lower dead center. The planting device is opened under the action of the control mechanism, the pot seedling is put into the hole in the soil, and the planting operation is completed. Then, the planting device is moved upward, the planting device is closed under the action of the control mechanism when it reaches a certain height, and the next working cycle begins. The planting device makes reciprocating rectilinear movement in the process of working, which improves the efficiency and reliability of a transplanter. However, the straight-line planting device has a velocity in the horizontal direction because it is moving forward with the transplanter. The inertia will cause the planting device to produce a scraping to the planted seedlings and, in this way, the planting seedling is not upright, maybe even inverted, and the quality of transplanting is reduced. In addition, this scraping is also not conducive to the pot seedling growth.
In order to prevent injury and scraping of the pot seedling caused by the horizontal velocity of the planting device, a kind of planting mechanism for a dry land transplanter is disclosed in Chinese Patent Publication CN101999268A, which includes a planetary carrier, a center wheel, a planetary wheel I, a planetary wheel II, a connecting rod I, a connecting rod II, rollers, a groove cam, and a duckbill planting device. By controlling the parameters of planetary gear ratio, CAM groove, planetary carrier, connecting rod length and difference of connecting rod length, the track of planting seedlings, receiving, carrying, punching, and planting suitable for a duckbill planting device can be obtained. The seedlings planted by the planting mechanism designed by the track are well upright and can avoid injury and scraping of the seedling. Unfortunately, the structure of this planting mechanism is complicated. The seedling upright degree can be guaranteed when the relative velocity of the duckbill planting device and the ground are zero. In particular, this planting mechanism has a slow planting speed and low work efficiency.